(Bloomberg) -- A U.S. congressman from New York who was charged with insider trading cannot review materials he says would show that investigators violated a constitutional provision limiting official inquiries into legislative matters, a judge ruled.

Christopher Collins, a member of the U.S. House of Representatives for a district outside Buffalo and an early backer of President Donald Trump, was charged last year with trading securities based on nonpublic information about an Australian biotechnology startup, Innate Immunotherapeutics Ltd. Also charged in the case were his son, Cameron Collins, and the father of Cameron’s fiancee. All three have pleaded not guilty.

Collins claims that seizures of evidence from his staff by law enforcement authorities violates the Speech or Debate Clause, which protects members of Congress from arrest and prosecution based on their political views.

Read More: Trump Backer Collins Halts Campaign Amid Insider Trading Charges

His legal team argued that he needs to see the materials -- statements, emails and social media posts by current and former congressional staffers -- to decide whether to ask for dismissal of charges against him or to block prosecutors from using the evidence.

U.S. District Judge Vernon Broderick denied the request in an order made public Wednesday, writing that “the searches did not involve congressional offices or official accounts, but were of the personal electronic devices and accounts” of the staffers.

The judge ruled in favor of Collins on one issue, excluding from the trial, set for February, evidence created during an investigation by the Office of Congressional Ethics, including an interview with the congressman.

Collins, the first House Republican to endorse Trump for president, is due to appear in federal court in Manhattan on Thursday.

The case is U.S. v. Collins, 18-cr-567, U.S. District Court, Southern District of New York (Manhattan).

To contact the reporter on this story: Bob Van Voris in federal court in Manhattan at rvanvoris@bloomberg.net

To contact the editors responsible for this story: David Glovin at dglovin@bloomberg.net, Peter Jeffrey

©2019 Bloomberg L.P.